Interestingly, I've been using card and online banking for so long that I seem to have internalized "money is the number stored in the bank's computer/my mental register". Recently I came into a steady flow of cash (long story), and I didn't want to go to the bank every damn week to deposit it, so I started paying for groceries and restaurants with that cash. It felt like giving away play money and getting real goods and services in exchange. "You mean I can give you some colored paper slips, and you'll just give me $100 worth of groceries? It doesn't reduce the money I have in the bank? And I'm not going to jail for this?" It was weird.